Start a user guide

docs/guide/index.rst

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 .. toctree::
    :maxdepth: 1
 
+   user_guide
    third_party

docs/guide/user_guide.rst

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+User guide
+==========
+
+Overview
+--------
+``napari-matplotlib`` contains a number of different ``napari`` Widgets. Each
+widget is designed to map one or more ``napari`` Layers on to a ``matplotlib`` plot.
+As an example, the `~.HistogramWidget` is used to
+map one or more Image layers on to a 1D histogram plot.
+
+The widgets split into two categories:
+
+Layer plotting
+~~~~~~~~~~~~~~
+These widgets plot the data stored directly in napari layers.
+Currently available are widgets to plot:
+
+- 1D histograms
+- 2D scatter plots (switching to 2D histograms for a large number of points)
+- 1D slice line plots
+
+To use these:
+
+1. Open the desired widget using the ``Plugins > napari-matplotlib`` menu in napari.
+2. Select the required number of layers using the napari layers list in the bottom left-hand side of the window.
+
+Features plotting
+~~~~~~~~~~~~~~~~~
+These widgets plot the data stored in the ``.features`` attribute of individual napari layers.
+Currently available are:
+
+- 2D scatter plots of two features against each other.
+
+To use these:
+
+1. Open the desired widget using the ``Plugins > napari-matplotlib`` menu in napari.
+2. Select a single layer that has a features table using the napari layers list in the bottom left-hand side of the window.
+3. Use the drop down menu(s) under the Matplotlib figure to select the feature(s) to plot.